Equivalent & Substitute Parts for 5ST 400 Glass Cartridge Fuse

Part Overview

The Bel Fuse Inc. 5ST 400 is a 400 mA, 250 V AC/DC slow-blow glass cartridge fuse in 5mm x 20mm package format, requiring a fuse holder for installation. This part is classified as obsolete. Due to its discontinued status, equivalent substitute parts from active product lines are necessary to maintain system functionality and ensure continued availability for new designs and field replacements.

Key Parameters

Parameter	Value
Current Rating	400 mA
Voltage Rating (AC)	250 V
Response Time	Slow Blow
Package / Case	5mm x 20mm
Fuse Type	Cartridge, Glass
Mounting Type	Requires Holder
Breaking Capacity @ Rated Voltage	35 A
Operating Temperature Range	-55°C to 125°C

Substitute Part Grouping Explanation

Substitution eligibility is determined by strict equivalence across the following critical parameters:

Current Rating: 400 mA (exact match required)
Voltage Rating (AC): 250 V (exact match required)
Response Time: Slow Blow (exact match required)
Package / Case: 5mm x 20mm (exact match required)
Fuse Type: Cartridge, Glass (exact match required)
Mounting Type: Requires Holder (exact match required)

Parts are classified into two categories:

Direct Equivalents: Parts meeting all critical parameters with identical electrical and mechanical specifications. These include 5ST 400-R (Bel Fuse Inc.), 0034.3113 (SCHURTER Inc.), 0218.400MXBP, 0218.400MXP, 0218.400TXP, and 0218.400VXP (all Littelfuse Inc.).

Parametric Equivalent: The 5TT 400-R (Bel Fuse Inc.) meets all critical parameters but features enhanced breaking capacity (100 A vs. 35 A) and higher melting I²t (1.65 vs. 0.81), making it suitable for applications requiring higher fault current protection.

Similar Parts: The 0034.2512 (SCHURTER Inc.) and 0239.400HXP (Littelfuse Inc.) share the same current rating, voltage, package, and response time but differ in secondary electrical characteristics or voltage specifications and are listed for reference only.

Parameter Comparison

Manufacturer Part Number	Manufacturer	Current Rating (mA)	Voltage AC (V)	Response Time	Package	Breaking Capacity (A)	Melting I²t	Product Status	RoHS Status
5ST 400	Bel Fuse Inc.	400	250	Slow Blow	5mm x 20mm	35	0.81	Obsolete	Non-compliant
5ST 400-R	Bel Fuse Inc.	400	250	Slow Blow	5mm x 20mm	35	0.81	Active	ROHS3 Compliant
5TT 400-R	Bel Fuse Inc.	400	250	Slow Blow	5mm x 20mm	100	1.65	Active	ROHS3 Compliant
0034.3113	SCHURTER Inc.	400	250	Slow Blow	5mm x 20mm	35	0.768	Active	ROHS3 Compliant
0218.400MXBP	Littelfuse Inc.	400	250	Slow Blow	5mm x 20mm	35	1.325	Active	ROHS3 Compliant
0218.400MXP	Littelfuse Inc.	400	250	Slow Blow	5mm x 20mm	35	1.325	Active	ROHS3 Compliant
0218.400TXP	Littelfuse Inc.	400	250	Slow Blow	5mm x 20mm	35	1.325	Active	ROHS3 Compliant
0218.400VXP	Littelfuse Inc.	400	250	Slow Blow	5mm x 20mm	35	1.325	Active	ROHS3 Compliant
0239.400HXP	Littelfuse Inc.	400	250	Slow Blow	5mm x 20mm	35	1.49	Active	ROHS3 Compliant

Engineering Selection Recommendations

Primary Recommendation: The 5ST 400-R (Bel Fuse Inc.) is the direct functional equivalent with active product status and ROHS3 compliance. It maintains identical electrical characteristics and package specifications as the obsolete 5ST 400, ensuring drop-in compatibility.

Alternative from Littelfuse Inc.: The 0218.400MXP, 0218.400TXP, and 0218.400VXP series provide equivalent performance with broader international certification coverage (CCC, CE, CSA, K-MARK, SEMKO, UL, VDE). These parts are suitable for applications requiring expanded regulatory approvals.

Alternative from SCHURTER Inc.: The 0034.3113 (FST 5x20 series) offers equivalent specifications with active status and ROHS3 compliance, providing supply chain diversity.

Enhanced Protection Option: The 5TT 400-R (Bel Fuse Inc.) provides the same current and voltage ratings but with doubled breaking capacity (100 A) and higher melting I²t (1.65). This part is appropriate for circuits requiring enhanced fault current withstand capability while maintaining the same thermal response profile.

Frequently Asked Questions (FAQ)

Q: Can I use 5ST 400-R as a direct replacement for the obsolete 5ST 400?

A: Yes. The 5ST 400-R is a direct equivalent with identical current rating (400 mA), voltage rating (250 V AC), response time (slow blow), and 5mm x 20mm package. Both require a fuse holder for installation. The primary difference is product status (active vs. obsolete) and RoHS compliance (ROHS3 vs. non-compliant).

Q: What is the difference between the Littelfuse 0218.400MXP and 0218.400TXP variants?

A: Both parts share identical electrical specifications: 400 mA, 250 V AC, slow-blow response, 5mm x 20mm package, and 35 A breaking capacity. The primary difference lies in regulatory certifications. The 0218.400TXP includes KC (Korea) certification, while the 0218.400MXP does not. Selection depends on target market requirements.

Q: Is the 5TT 400-R a suitable substitute for the 5ST 400?

A: The 5TT 400-R meets all critical electrical and mechanical parameters (400 mA, 250 V AC, slow blow, 5mm x 20mm). However, it features enhanced breaking capacity (100 A vs. 35 A) and higher melting I²t (1.65 vs. 0.81). Use this part only if your circuit design requires or can accommodate higher fault current protection levels.

Q: Why do some substitute parts have different melting I²t values?

A: Melting I²t is a secondary electrical characteristic that affects thermal response under fault conditions. While all listed direct equivalents maintain the same slow-blow response classification and current rating, variations in melting I²t reflect differences in internal fuse element design between manufacturers. This does not affect basic substitution eligibility for standard applications.

Q: Can I substitute the 0034.2512 for the 5ST 400?

A: The 0034.2512 shares the same current rating (400 mA), voltage (250 V AC), package (5mm x 20mm), and response time (slow blow). However, it is classified as a medium-blow fuse with different DC voltage rating (125 V DC vs. DC unspecified) and lower melting I²t (0.632 vs. 0.81). This part is listed for reference only and is not recommended as a direct substitute without circuit-level analysis.

Q: What certifications should I prioritize when selecting a substitute?

A: The original 5ST 400 carries CE, CSA, IMQ, SEMKO, UL, and VDE certifications. The 5ST 400-R maintains these certifications plus CCC and cURus. For applications requiring specific regional compliance, verify that your selected substitute carries the required certifications for your target market.

Q: Are all substitute parts RoHS compliant?

A: All active substitute parts listed (5ST 400-R, 5TT 400-R, 0034.3113, and all Littelfuse 0218 and 0239 series) are ROHS3 compliant. The original 5ST 400 is RoHS non-compliant. This is a key advantage of transitioning to any of the listed active substitutes.

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